To use a custom control, you need a field with special attributes to be linked to the “publish” button.
if you don’t want to display this field, you can generate a hidden field like that :
class WP_Test_2_Customize_Control extends WP_Customize_Control
{
public function render_content()
{
?>
<input
id="<?php echo htmlspecialchars("_customize-input-{$this->id}");?>"
type="hidden"
<?php $this->input_attrs();?>
<?php if (!isset($this->input_attrs["value"])) {?>
value="<?php echo htmlspecialchars($this->value());?>"
<?php }?>
<?php $this->link();?>
/>
<?php
}
}
then, when you modify values in the other fields, you put values in this field with JavaScript and then trigger the change event on this hidden field.